Plate clamping means



Jan. 22, 1957 HELLER 2,778,307

PLATE CLAMPING MEANS Filed April 14, 1953 3 Sheets-Sheet l INVENTOR Jan. 22, 1957 F. HELLER PLATE CLAMPING MEANS 3 Sheets-Sheet 2 Filed April 14, 1953 INVENTOR ZZZ! l J ///Z%/////% V Jan. 22, 1957 Filed April 14, 1953 F. HELLER PLATE CLAMPING MEANS 3 Sheets-Sheet 5 ATTORNEYS PLATE CLAMPIN G MEANS Franz Heller, Mount Vernon, N. Y., assignor, by mesne assignments, to American Type Founders Co., Inc., Elizabeth, N. 3., a corporation of Delaware Application April 14, 1953, Serial No. 348,706

2 Claims. (Cl. 101-4151) This invention relates to clamping devices for securing lithographic printing plates or the like in position on a rotary printing cylinder.

It is the primary object of this invention to provide a plate clamping device by means of which a plate may be secured to or detached from a printing cylinder easily, accurately, and with uniform tension to insure satisfactory printing. It is, of course, desirable that any plate clamping means be simple in construction and capable of quick actuation and adjustment so that the down time of a press can be reduced with a resutling increase in production.

It is another object of this invention to provide plate clamping means for printing cylinders so constructed and arranged that when a plate is secured to the cylinder, the gap between plate ends on the periphery of the cylinder is very small.

It is yet another object of this invention to provide an improved plate clamping mechanism which is adapted to effect continuous support for the plate, whereby the full area of the plate lies solidly on the cylinder surface even up to the slight gap which separates the endsof the effective plate surface, thus preventing crystallization of the plate which would result from repeated flexing of any unsupported plate area as the cylinder rotates in contact with the other members of the printing couple or the inking and wetting systems.

It is a further object of this invention to provide plat clamping means which can be easily adjusted from one end of the cylinder without the necessity of removing the cylinder from its mounting or passing tools or parts through such cylinder mounting. Also, by virtue of the provision of the novel clamping means, it is not necessary that any of the parts of the adjusting or actuating means pass through the cylinder bearings.

With these and other objects in view, the invention consists in the construction and novel combination and arrangement of parts hereinafter described, illustrated in the drawings and set forth in the claims, it being understood that various changes in the form, proportion, and minor details of construction, within the claims, may be resorted to without departing from the spirit of the invention or sacrificing any of the advantages thereof.

In the drawings: a V Figure 1 is an end elevation, partly broken away, of a cylinder provided with my improved clamping means in the closed position with a plate secured'thereto;

Figure 2 is a fragmentary cross-section taken along line 22 in Figure 1;

Figure 3 is a fragmentary cross-section taken along the line 33 of Figure 2;

Figure 4 is a fragmentary cross-section taken along the line 4-4 in Figure 3;

Figure 5 is a fragmentary cross-section taken along the line 5-5 in Figure 4;

Figure 6 is a plan view of a cylinder end showing the clamping mechanism locking means;

Figure 7 is an elevation, with cylinder and pinion shaft frame broken away, of the plate jaw together with its rack and pinion mechanism prior to lockingthe plate on the cylinder; and g nited States Patent 0 Figure 8 is an elevation, with cylinder and pinion shaft broken away, of the plate jaw together with its rack and pinion mechanism in locked position.

Referring to the drawings, and in particular to Figure 1, an end view of a typical cylinder used in lithographic presses is shown. The cylinder body, designated generally at A, is provided with two adjoining longitudinal recesses or gaps shown in Figure 3 at 1 and 2. Within these recesses the plate clamping means hereinafter described is positioned. About the cylinder a flexible printing plate or blanket 6 is positioned. The plate has a head end 6a and a tail end 6b, these ends being secured in the cylinder gap 2. When so secured, the tail end 6b is movable relative to head end 6a so that the plate is placed in a state of tension, and fits snugly about the periphery of cylinder A. Within gap 1 frame 12 is positioned. Frame 12 houses mechanism for imparting motion to tail end 6b.

The tail and head ends of the plate are provided with longitudinal securing bars 3, these bars being fixed on the plate ends by means of screws 4 or the like as is best seen in Figure 4. A chordal wall of gap 2 has a longitudinal extending slot 5 machined therein. This slot is designed to receive securing bar 3 fixed on the head end 6a of the printing plate. The plate or blanket 6 is then bent about the adjacent gap edge at B, wrapped around the printing cylinder, and its tail end 6b is received by the clamping mechanism which is designed to place the plate in a state of tension thereby preventing withdrawal of bar 3 of head end 6a from slot 5.

Tail end 612 of the plate is detachably secured to jaw 7 by reception of its longitudinal bar 3 in recess 8 of the jaw. Jaw 7 extends longitudinally of the printing cylinder A and is guided for movement outwardly of the cylinder along line C. This guide means includes guide plate 9 secured in recess 2 for sliding engagement with one chordal face of jaw 7, and pins 10 extending from an opposite chordal face of jaw 7 for reception in guide slots 11 on frame 12.

When jaw 7 is fully retracted in the cylinder, as shown in Figure 3, its arcuate face 7a serves to partially close the gap 2, leaving a thin longitudinal slit at point B on the cylinder periphery. It is through this slit that plate.

ends 6a and 6b pass to their points of securement within gap 2.

1 The jaw is movable outwardly of the cylinder along chordal line C. This line is directed outwardly of the cylinder at an angle to the cylinder diameter BF which intersects the gap edge at B. Such direction of movement must also be away from plate end 6a so that as the jaw 7 ismoved away frompoint B the tail end of the plate is released from its state of tension and bulges outwardly of jaw 7 to follow the line defined by D. Between the point of tension B and the point E where the line of travel D of plate 6 intersects the line of travel C of jaw 7, plate 6 is in a state of "relaxation. When in such state, bar 3 of plate end 6b may be removed from the recess 8 thus permitting complete removal of the plate from cylinder A.

The means for adjusting the position of jaw 7 is incorporated in the frame 12 fixed in gap 1 as by screws 13. Rotatablymounted within member 12 and running the entire length thereof is a shaft 14 upon which are keyed three pinions, 15a, 15b and 150. These pinions are adapted to meshwith racks 16a, 16b and 16c, respectively, on jaw 7. Consequently, rotation of shaft 14 will impart movement along line C to jaw 7. Referring more particularly to. Figures 2 and 4, the shaft 14 extends through one end of the printing cylinder proper and has a worm wheel. 17 keyed to its end. The worm wheel meshes with a screw 18 the hex-shaft 19 (Figure 1) of which passes through the cylinder end plate 20 and is experiphery oflthe end plate... V. r

To place the printing plate under a state of uniform tension so that it is more accurately positioned, a novel rack arrangement is provided. Referring to Figures 7 and 8, it will be seen'that three rack surfaces, 16a, 16b and 160, are machined on a chordal face of jaw 7-. 'While the pitch of the teeth. on all racks and piuions is equal, the racks are slightly displaced at varying distan'cesfrom the innermost edge 7b on the cho'rdal face. Thus in Fig ure 7 it may be seen that the teeth on rack 16c begin on edge 7b and extend upwardly, but the teeth onrack 16!)- extend upwardly from a point slightly above edge 71;. Rack 16a, in turn, is displaced above edge 7b at approximately twice the distance which rack 16b is displaced, displacement of the racks increasing the further they are removed from worm wheel 17. Due to this arrangement, the jaw when retracted outwardly of the cylinder is not parallel to its seating. surface on. the bottom of gap 2, but is lower at the jaw end furthest removed from worm wheel 17. When the jaw is moved downwardly into slot 2, as shown in Figure 7, this far .end of jaw member 7 will contact. the bottom of slot 2 in advance of the jaw end nearest worm wheel 17. If the operator continues to rotate worm wheel 17, shaft 14 will twist in order to cause that end of the jaw nearest the worm wheel to seat atthe bottom of slot 2 as in Figure 8. Such twisting,

or torsion, on the shaft is a desirable effect, for it serves to offset the tendency of the shaft end furthest removed from worm wheel 17 to twist in the opposite direction when a printing plateis locked on the cylinder. However, it must be borne in mind that the degree of twist of the shaft is quite small and the differential positioning of therack surfaces is thus also of small magnitude. Whatever minor lateral angling of the jaw member which may occur will thus be readily accommodated by the normal tolerance and negligible back-lash in the mounting of this member.

To insure that jaw 7 is firmly locked against movement, a keeper 21 is provided in a small recess on the cylinder end plate adjacent hex-shaft 19. This keeper, shown in Figure 6, is secured in the slot by bolt 22 passing through elongated slot 23 in the keeper. By'partially unscrewing the bolt, the keeper is in sliding relation within the end plate. Keeper 21 has a hexangular insertat its forward end so formed that when it reaches its forward point of travelthe insert registers with hex-shaft 19. By securing the keeper at its forward point of travel shaft 19 can be locked against rotation thereby. placing the en tire clamping mechanism in a locked condition.

In summary, to secure plate 6 to the cylinder the retaining bar 3 of the plate head end 6a is inserted in slot 5. The plate is then wrapped about the cylinder A, jaw 7 being in an open position at some point between B and E. The bar 3 on the tail end 611 of the plate is then inserted in recess 8. Next, a hex-wrench or the like is fitted on shaft 19 and the shaft is rotated so that jaw '7 is moved inwardly to the position shown in Figure 8. At this point the gap at B between the plate ends on the cylindrical periphery is at a minimum. Shaft 19 is then locked against rotation by bringingslide 21 into register with it, and by tightening screw 22 so that the slide is held fast.

To remove the plate from cylinder A it is merely necessary to unlock shaft 19 by bringing slide 21 out of register with it, and then rotate the shaft so that jaw 7 is moved outward along line BE to a point between B and E. It is then possible to remove bar 3 on end 6b from slot 8, unwrap the plate from cylinder A and remove bar 3 on head end 6a from slot 5'.

It is to be noted that in the clamped position, plate 6 is supported about the entire periphery of the cylinder by the cylinder body and by the arcuate face 7a of the jaw. Those portions of the plate lying within the cylinder are supported by chordal wall of the cylinder gap and the radial wall of the jaw.. In this manner, crystallization of the: plate which would result upon repeated flexing of an.

unsupported plate area as the plate rotates iseliminatedt to which the invention relates.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a clamping device for securing a flexible printing plate to the periphery of a rotary printing cylinder which has a longitudinally extending gap on its periphery, in combination, means for detachably securing one end portion of said plate to said cylinder within said gap whereby the end portion is bent aroundv one of the edges of said gap, a jaw member detachably receiv-- ing, the other end portion of said plate and movably disposed within said gap, means for guiding a face on said jaw member for movement in a chordal direction at an angle with respect to the cylinder diameter which intersects said gap edge, said direction of movement diverging outwardly of said diameter away from said gap edge and said first mentioned end portion of the plate, a plurality of toothed racks spaced longitudinally on said jaw face, a shaft rotatably mounted in the cylinder, means at one end of said shaft for rotating it, a plurality of pinions fixed along the shaft for meshing engagement with said racks whereby rotation of said shaft moves said jaw, said racks being so disposed on said jaw face that the displacement between each rack and the edge of said jaw face innermost of the cylinder is progressively greater the further such rack is removed from said shaft rotating means.

2'. In a clamping device for securing a flexible printing plate to the periphery of a rotary printing cylinder which has a longitudinally extending gap on its periphery, one side wall of which extends at a re-entrant angle relative to the contiguous portion of said periphery, in combination, an elongated bar for attachment to the end portion of the plate, a slot in said gap side wall, means for detachably securing said bar in said slot to thereby detachably secure the end portion of said plate to said cylinder within said gap so that said end por tion is bent around one of the edges of said gap, a jaw member movably disposed within said gap, said jaw member having an arcuate face adapted to support a portion of the. printing plate, another face adjacent said arcuate face extending in a radial direction, and a short face opposite to said radial face extending in a chordal direction at an angle with respect to a'cylinder diameter through said radially extending face, said radially extending facehaving, a slot therein, a second elongated bar. for attachment to the other end portion of said plate, means for detachably securing said second elongated bar in the sloton said radial face, and means for guiding said jaw member along an axis parallel to the plane of said further face, the direction of movement of said jaw diverging, outwardly of the cylinder diameter through said radial face and away from the edge of said gap defined by said re-entrant side wall and the contiguous. portion of the peripheral cylinder wall.

References Cited in the file of this patent UNITED STATES PATENTS 

